Fish poop exposes what eats the destructive crown-of-thorns starfish
Identifying predators of the coral polyp slurping starfish could be key to protecting reefs
![Frederieke Kroon diving](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2020/06/052720_JB_thorns-fish_feat.jpg?fit=1028%2C579&ssl=1)
Biologist Frederieke Kroon gets a closer look at a crown-of-thorns starfish while diving on the Great Barrier Reef. This starfish devours corals, so when its population booms, that can devastate reefs.
David Westcott/CSIRO
Adorned with spikes and toxins, crown-of-thorns starfish aren’t an easy meal. In fact, it’s long been thought that few animals could eat them. But an analysis of fish poop and stomach contents from dozens of Great Barrier Reef species reveals a surprising number of fish able to gulp down these prickly prey, researchers report May 18 in Scientific Reports.
That’s good news for coral reefs. Crown-of-thorns starfish (Acanthaster cf. solaris) have an appetite for living coral polyps. As they crawl over the reef, the starfish liquefy polyps with digestive enzymes, sponging up the nutrients and leaving behind a coral skeleton. Since 1962, periodic starfish population booms on the Great Barrier Reef have caused widespread coral death. By identifying which fish species can stomach a thorny diet, the new study reveals a possible way to suppress crown-of-thorns outbreaks.
Until now, the crown-of-thorns’ list of known natural predators was very short. Giant tritons (Charonia tritonis) — huge sea snails — were documented starfish slayers, injecting crown-of-thorns with venomous saliva and sanding down their spiny exterior with a rasping tongue. And while dozens of reef fish had been observed eating crown-of-thorns, most of these starfish were injured or dead.
Yet occasional starfish population booms suggest something is normally eating live, healthy crown-of-thorns and keeping their numbers in check. So to find the mystery predators, Frederieke Kroon, a biologist at the Australian Institute of Marine Science (AIMS) in Townsville, looked to the guts and feces of reef fish for answers.